The invention relates to measurement of the inclination of a borehole, and more particularly to a transducer array particularly suited therefor.
In drilling boreholes, as for the production of oil and gas, it is desirable to know the course of the hole and the position of a drilling apparatus in the hole. This information is most important in directional drilling in which a borehole is drilled to some predetermined point below the earth surface and horizontally displaced from the surface location. An important example of such directional drilling is found in drilling wells from offshore platforms. There it is a common practice to build a large drilling platform that is permanently secured to the ocean floor and from which a multiplicity of wells are drilled. Because of the number of wells that are drilled from a single platform, it is necessary to drill the holes laterally from the platform in order that earth formations containing petroleum reservoirs may be penetrated at desired locations. This procedure permits production from as great an area as possible by equipment located on a single platform.
In order to determine the course of a borehole it is necessary to know two pieces of information, the inclination of the borehole with respect to the vertical, and the azimuthal direction of the inclined hole. A common means of measuring inclination and azimuth is disclosed in U.S. Pat. No. 3,791,043. This patent discloses both a mercury pendulum switch and a resistive type strain gauge. In each instance these devices are arranged along the axes of an orthogonal coordinate system. The patent also discloses three fluxgates in a mutually perpendicular configuration for measuring components of the earth's magnetic field.